FileChannel类的简单用法

清单一：

1. importjava.io.*;
2. importjava.nio.*;
3. importjava.nio.channels.*;
4. publicclassGetChannel
5. {
6. privatestaticfinalintBSIZE=1024;
7. publicstaticvoidmain(String[]args)throwsIOException
8. {
9. FileChannelfc=newFileOutputStream("data.txt").getChannel();
10. fc.write(ByteBuffer.wrap("sometxt".getBytes()));//write()Writesasequenceofbytesto
11. //thischannelfromthegivenbuffer
12. fc.close();
13. fc=newRandomAccessFile("data.txt","rw").getChannel();
14. fc.position(fc.size());//abstractFileChannelposition(longnewPosition)
15. //Setsthischannel'sfileposition.
16. fc.write(ByteBuffer.wrap("somemore".getBytes()));
17. fc.close();
18. fc=newFileInputStream("data.txt").getChannel();
19. ByteBufferbf=ByteBuffer.allocate(BSIZE);//staticByteBufferallocate(intcapacity)
20. //Allocatesanewbytebuffer.
21. //一旦调用read（）来告知FileChannel向ByteBuffer存储字节，就必须调用缓冲器上的filp（），
22. //让它做好别人存储字节的准备（是的，他是有点拙劣，但请记住他是很拙劣的，但却适于获取大速度）
23. //
24. fc.read(bf);//Readsasequenceofbytesfromthischannelintothegivenbuffer
25. bf.flip();
26. while(bf.hasRemaining())
27. System.out.print((char)bf.get());
28. }
29. }

清单二：

1. //Copyingafileusingchannelsandbuffers;
2. importjava.io.*;
3. importjava.nio.*;
4. importjava.nio.channels.*;
5. publicclassChannelCopy
6. {
7. privatestaticfinalintBSIZE=1024;
8. publicstaticvoidmain(String[]args)throwsIOException
9. {
10. if(args.length!=2)
11. {
12. System.out.println("argument:sourcefiledestfile");
13. System.exit(1);
14. }
15. FileChannel
16. in=newFileInputStream(args[0]).getChannel(),
17. out=newFileOutputStream(args[1]).getChannel();
18. ByteBufferbb=ByteBuffer.allocate(BSIZE);
19. while(in.read(bb)!=-1)
20. {
21. bb.flip();
22. out.write(bb);
23. bb.clear();//prepareforreading;清空缓冲区；
24. }
25. }
26. }

清单三

1. importjava.io.*;
2. importjava.nio.*;
3. importjava.nio.channels.*;
4. publicclassTransferTo
5. {
6. publicstaticvoidmain(String[]args)throwsIOException
7. {
8. if(args.length!=2)
9. {
10. System.out.println("argument:sourcefiledestfile");
11. System.exit(1);
12. }
13. FileChannel
14. in=newFileInputStream(args[0]).getChannel(),
15. out=newFileOutputStream(args[1]).getChannel();
16. //abstractlongtransferTo(longposition,longcount,WritableByteChanneltarget)
17. //Transfersbytesfromthischannel'sfiletothegivenwritablebytechannel.
18. in.transferTo(0,in.size(),out);
19. //or
20. //usingout
21. //abstractlongtransferFrom(ReadableByteChannelsrc,longposition,longcount)
22. //Transfersbytesintothischannel'sfilefromthegivenreadablebytechannel.
23. //out.transferFrom(in,0,in.size());
24. }
25. }